Global prevalence of intestinal parasites in cancer patients: a systematic review and meta-analysis.

Introduction

Infection with intestinal parasites is prevalent globally, particularly in developing countries [ 1 ]. Intestinal parasite infection (IPI) is a significant cause of diarrhea and a clinical factor contributing to infections in both immunocompetent and immunocompromised individuals, including those with diabetes mellitus, malignancies, steroid use, and human immunodeficiency virus (HIV) infection. However, cancer patients are at increased risk of infection [ 2 , 3 ].

Parasitic diseases fall within the category of neglected tropical diseases and pose a significant public health challenge because of their impact on morbidity and mortality among various population groups with immunocompromised conditions [ 4 , 5 ]. In particular, opportunistic infections pose significant challenges for immunocompromised individuals, including those receiving cancer treatment [ 6 ]. Intestinal parasites can lead to severe morbidity and mortality in cancer patients. The compromised immune systems of these patients, resulting from either the cancer itself or treatments such as chemotherapy and radiation therapy, increase their vulnerability to intestinal parasite infections [ 7 ].

Patients who receive cancer chemotherapy have an increased probability of acquiring parasitic infections, generally with a high degree of severity [ 8 ]. Among cancer patients, immunosuppression due to the disease itself or the therapeutic agents used increases the risk of intestinal parasitic infections [ 9 ].

Enteric protozoan parasites are among the most prevalent parasitic diseases that can lead to infections, especially in individuals with weakened immune systems, such as organ transplant recipients, cancer patients, and those with common variable immunodeficiency (CVID) [ 10 ]. Notably, Cryptosporidium spp., Blastocyst hominis, and Strongloide stercoralis are significant intestinal parasites because of their opportunistic nature, often causing severe complications in immunocompromised patients [ 11 ].

Cancer is a major cause of death worldwide, particularly in developing countries, and occurs through the uncontrolled division of normal cells to form abnormal growths or tumors [ 12 ]. It is expected that the number of deaths from cancer worldwide will continue to increase to approximately 11 million deaths in 2030 [ 13 ]. Treatments such as chemotherapy and radiotherapy increase the risk of opportunistic infections, including those caused by intestinal parasites, in cancer patients. Research has shown that immunocompromised individuals are at greater risk of experiencing chronic diarrhea as a result of these infections [ 14 ]. In 2008, approximately 2 million new cancer cases (16%) worldwide were attributable to different types of infection. If these infections could be prevented and/or treated, it is estimated that there would be approximately 23% fewer cancers in less developed regions of the world and approximately 7% fewer cancers in more developed regions [ 15 ].

Although primary studies have investigated the prevalence and impact of intestinal parasites in cancer patients, the results vary widely due to differences in methodology, sample size, and regional focus. Furthermore, there is limited information on the global combined prevalence of these parasites in cancer patients across different countries. To determine the overall prevalence, it is essential to systematically gather and analyze data from existing primary studies. By integrating findings from various countries worldwide, we can provides representative understanding the pooled prevalence of intestinal parasites in cancer patients, which will generate strong evidence of evaluating current control and preventive strategies for decision making. Moreover, understanding the relationship between intestinal parasites and cancer is essential for choosing appropriate treatments that effectively eradicate infections. Therefore, the aim of this systematic review and meta-analysis was to estimate the pooled prevalence of intestinal parasite infection among cancer patients.

Methods

Study protocol registration

The results of the current systematic review and meta-analysis were reported based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines [ 16 ] ( S1 Table), which outlines the design, analysis, and interpretation of all eligible studies. Furthermore, the study’s protocol was registered in the International Prospective Register of Systematic Reviews (PROSPERO; CRD42024621432).

Data source and systematic search strategy

We conducted a search through several databases, including PubMed/ MEDLINE, Science Direct, Scopus, EMBASE, African Journal Online, the Cochrane Library, and Web of Science. In addition, Google Scholar, Google search, institutional or research repositories and cross-check of identified primary studies were applied to obtain relevant articles. A literature search was conducted using search terms separately and in combination with Boolean operators “AND” and “OR”. The following search strategy has been developed for PubMed database and customized for other electronic databases: ((((((((((((((Intestinal disease) OR (Gastrointestinal microbes)) OR (Gastrointestinal tract)) OR (Enteric parasites)) OR (Parasites)) OR (Parasitic)) OR (Protozoa)) OR (Helminths)) AND (Prevalence)) OR (Epidemiology)) OR (Frequency)) AND (Cancer patients)) OR (Neoplasms)) AND (worldwide [MeSH Terms]).

Eligibility criteria of studies

Inclusion criteria

The inclusion criteria for eligible studies were as follows: the study population was restricted to cancer patients, and only full-text articles published in English from countries around the world were considered. We included preprints and peer-reviewed original articles with no limitations on geography or publication date, up to 15 December 2024. Observational studies (such as cross-sectional, case-control, and cohort studies) that reported the prevalence of intestinal parasites among cancer patients were eligible for inclusion. This systematic review and meta-analysis encompassed any solid tumors, including invasive ductal carcinoma, invasive lobular carcinoma, colorectal carcinoma in situ, breast cancer, mixed types of cancer, and hematological malignancies.

Exclusion criteria

The current study excluded any studies that did not report the detection of intestinal parasites in cancer patients, including those involving non-cancerous immunocompromised patients and/or immunocompetent individuals, and articles published in non-English language. Moreover, animal studies and those with unclear or ambiguous information were also excluded. Reviews, case reports, conference abstracts, registered clinical trial protocols, letters to the editor, and personal opinions were not considered for inclusion.

Study selection and data extraction

The initial screening was conducted based exclusively on the titles and abstracts of the papers. After eliminating duplicates, two reviewers independently assessed the titles and abstracts of the remaining records for potential inclusion. In cases of disagreement, a third reviewer was consulted. Subsequently, suitable full-text copies of the articles were obtained and evaluated for eligibility. All studies that were excluded were documented, along with the reasons for their exclusion.

The data collection form was created using Microsoft Excel (version 2010; Microsoft Corp., Redmond, WA, USA). We systematically extracted information regarding study characteristics and data on intestinal parasites among cancer patients from the articles. This included details such as the study site/region, study period, study designs, sample size, diagnostic methods, types of cancer, and the number of positive cases of intestinal parasite infections among cancer patients. The data extraction was performed independently by two reviewers, with any discrepancies resolved by a third reviewer.

Outcome of interest

The primary aim of this study was to estimate the global pooled prevalence of intestinal parasite infections among cancer patients. This prevalence was calculated by dividing the number of cancer patients who tested positive for intestinal parasites by the total number of cancer patients and then multiplying that result by 100.

Quality assessment

The quality of the papers was another critical criterion for including relevant articles. In this systematic review and meta-analysis, we utilized the Joanna Briggs Institute (JBI) Critical Appraisal Checklist for Studies Reporting Prevalence Data [ 17 ]. Articles that received scores of 4–6 and 7–9 were classified as moderately and highly qualified, respectively. Consequently, articles scoring 0–3 points were excluded from this systematic review (Table S2 ). Furthermore, a score of nine indicates a ‘completely low risk of bias’.

Data synthesis and statical analysis

In the present study, data imported from Microsoft Excel 2010 were analyzed using STATA version 11 software. The prevalence of intestinal parasites among cancer patients was assessed by calculating the pooled prevalence along with the 95% confidence interval (CI) using a random effects model. Furthermore, odds ratios (OR) and their corresponding 95% CI were computed for each individual study.

Heterogeneity among the studies was evaluated using the I² method. This approach categorizes heterogeneity as follows: 0% indicates no heterogeneity; < 25% signifies low heterogeneity; 25–50% denotes moderate heterogeneity; 50–75% represents significant heterogeneity; and > 75% indicates high heterogeneity [ 18 ]. Additionally, Egger’s regression test was employed to detect small study effects and potential publication bias. A funnel plot was also utilized to assess the likelihood of publication bias during the analysis. The results are presented as forest plots, illustrating the differences in prevalence rates of intestinal parasites among cancer patients, quantified by odds ratios (OR) and 95% confidence intervals (CI). A p-value of < 0.05 was deemed statistically significant.

Results

Selection of studies

In summary, our primary systematic search yielded 10,452 articles. Following an initial screening of titles and abstracts, along with the removal of duplicates, 1,343 articles underwent a comprehensive review by trained investigators. Ultimately, 34 papers met the criteria for inclusion in this systematic review and meta-analysis (Fig. 1 ).

Fig. 1 PRISMA chart of the selection steps of the included studies

Characteristics of the included studies

The main characteristics of the included papers were that they were published between 2006 and 2023 and included 4752 study participants. In terms of geographical location, the 34 studies originated from four different regions: seven (848 individuals) papers from African countries, 23 from Asia, two from Europe, and two from South America. Among the 34 studies included in this review, nine focused on a single intestinal parasite infection in cancer patients, whereas the remaining studies reported multiple intestinal parasite infections among cancer patients; in particular, Blastocystis hominis emerged as the most commonly associated intestinal parasite in this population.

A total of 19 studies focused on patients with solid cancer types such as: Colorectal cancer in Poland [ 19 ], Lung, Breast and Colorectal cancers in turkey [ 20 ], Colorectal cancer in United Arab Emirates [ 21 ], Breast, Prostate, Lung, CA of GIT, ovarian, and choriocarcenoma cancers in Nigeria [ 22 ], Colorectal in Nigeria [ 23 ], breast cancer in Brazil [ 24 ], GIT cancer in Brazil [ 25 ], colorectal cancer in Iran [ 10 ], Gastrointestinal cancer in china [ 26 ], GIT cancer in Egypt [ 27 ], Bladder, Cervical, Colorectal, Lung, Ovarian, and Thyroid cancers in Ethiopia [ 28 ], Colorectal cancer in Uzbekistan [ 29 ], while 6 studies targeted patients with hematological malignancies (HMs) like lymphoma/ leukemia in Egypt and Nepal [ 1 , 30 ], Nutroblastoma, acute meyloblastic leukemia (AML), acute lymphoblastic leukemia (ALL), Ewing sarcoma, Osteosarcoma, Nutfibroplastosis, and Hemophagocytic lymphohistiocytosis (HLH) in Iran [ 31 ], AML, ALL, diffuse large B-cell lymphoma, Plasma cell myeloma, Myelodysplastic syndrome, and Burkett’s lymphoma in Poland [ 32 ], Leukemia in Iran [ 33 ], and Lymphoma, Ewing sarcoma, and Multiple myeloma in Iran [ 34 ].

The 9 studies included mixed populations with both solid and hematological malignancies such as:- Medulloblastoma, Ewing sarcoma, Osteosarcoma, Angiofibroma, Germinoma, ALL, AML, Lymphoma in Malaysia [ 7 ], Breast-lymph node, Prostate, GIT, Brain, Spinal, AML, CLL, multiple myeloma, ALL, Lymphoma, in Iran [ 35 ], Blood, GIT, Lung, Brain, Cervical, Colon, Skin, Gonads, and Breast cancers in Iraq [ 36 ], cancers location (Hematological, Digestive System, Breast, Respiratory System, Bone and Soft Tissue, Nervous System, Excretory System, and Genital System) in Turkey [ 9 ], Lymphoma, Leukemia, Multiple myeloma, B-cell lymphoma, Lung cancer, Colon cancer, Cholangiocarcinoma, Adenocarcinoma, Choriocarcenoma, Breast cancer, Gastrointestinal cancer, and Ovarian cancer, Iran [ 6 ], the remaining 4 studies used mixed population don’t specify cancer types rather they reported general solid and hematological malignancy [ 37 – 40 ].

In terms of epidemiological design, 18 studies were cross-sectional, 11 employed a case-control design, and 2 were cohort studies. Among all the included studies, 15 assessed intestinal infections via fecal microscopy, and the remaining studies used microscopic, culture, or molecular techniques. The sample size ranged from 15 to 387 individuals, and the oldest study was conducted in 2006 [ 25 ] ( Table 1 ) .

Table 1 The main characteristics of studies included in this systematic review and meta-analysis, 2024 Author, year Study year Country Study design IP-diagnostic method Cancer types Sample size Prevalence (%) Q Score (9%) Reference (Abdel-Magied et al., 2016) 2012–2014 Egypt Cross-sectional Microscopy and culture HM 145 85.5 9 [ 30 ] (Ali et al., 2022) 2019–2021 Egypt Cross-sectional Microscopy, Culture, and PCR Solid 100 52 9 [ 66 ] (Bahadorizadeh et al., 2024) 2022–2023 Iran Cross-sectional Microscopy and PCR Mixed 158 31.6 9 [ 6 ] (Banihashemi et al., 2020) 2018 Iran Cross-sectional Microscopy and PCR Mixed 250 4.8 8 (Berahmat et al., 2017) 2015–2016 Iran Case control Microscopy and PCR HM 132 3.8 9 [ 33 ] (Bora et al., 2016) 2016 India NR Microscopy Solid 15 80 8 [ 67 ] (El-Badry et al., 2019) 2013–2015 Egypt Cross-sectional Microscopy and PCR Mixed 137 6.6 8 [ 38 ] (Esteghamati et al., 2019) 2016–2017 Iran Cross-sectional Microscopy Solid tumor 85 25.9 8 [ 10 ] (Heydari et al., 2021) 2013–2014 Iran NR Microscopy and PCR Solid 54 24 8 [ 68 ] (Inah et al., 2022) 2022 Nigeria Cross-sectional Microscopy Solid 136 34.9 9 [ 22 ] (Jeske et al., 2017) 2017 Brazil NR Microscopy Solid 71 61.6 8 [ 24 ] (Kaplan et al., 2020) 2019 Turkey Cross-sectional microscopy Mixed 11 38.7 9 [ 9 ] (Knapp et al., 2019) 2018 Nigeria cohort Microscopy and serology Solid 139 49.6 9 [ 23 ] (Labania et al., 2023) 2022 United Arab Emirates Case control Microscopy and PCR Solid 52 63.4 9 [ 21 ] (Lanocha et al., 2022) 2017–2018 Poland Case-control Microscopy and serology HM 50 16 8 [ 32 ] (Machado et al., 2008) 2006 Brazil Case control Microscopy and Serology Solid 33 24.2 8 [ 25 ] (Mahmoudi et al., 2020) 2017 Iran Cross-sectional Microscopy Solid 362 11.3 9 [ 69 ] (Mohammadi-Ghalehbin et al., 2017) 2015 Iran Cross-sectional Microscopy HM 100 10 8 [ 34 ] (Mohamed et al., 2017) 2013–2015 Saudi Arabia Case control Culture and PCR Mixed 138 54.8 9 [ 40 ] (Mirzaei et al., 2021) 2018–2019 Iran Cross-sectional Microscopy and culture Mixed 188 12.2 9 [ 37 ] (Nasir et al., 2020) 2019 Iraq Cross-sectional Microscopy and serology Mixed 300 17 9 [ 36 ] (Neamah, 2021) 2020 Iraq Case control Microscopy Solid 387 25.06 9 [ 70 ] (Nooshadokht et al., 2017) 2016 Iran Cross-sectional Microscopy and PCR Mixed 59 15.28 8 [ 39 ] (Salehi et al., 2018) 2016–2017 Iran Cross-sectional Microscopy Solid 150 21.3 9 [ 71 ] (Salehi Kahyesh et al., 2020) 2019 Iran Cross-sectional Microscopy HM 52 38.38 8 [ 31 ] (Seleem et al., 2024) 2023 Egypt Case-control Microscopy and culture Solid 100 45 9 [ 27 ] (Singh et al., 2024) 2022–2023 Nepal NR Microscopy HM 100 8 8 [ 1 ] (Siti Farah Norasyikeen et al., 2024) 2023 Malysia Case control Microscopy Mixed 134 32.1 9 [ 7 ] (Sitotaw et al., 2022) 2020 Ethiopia Cross-sectional Microscopy Solid 41 17 8 [ 28 ] (Sulzyc-Bielicka et al., 2021) 2009–2014 Poland Case control Microscopy and PCR Solid 202 12.15 9 [ 19 ] (Toychiev et al., 2018) 2015–2017 Uzibekistan Cohort Microscopy Solid 200 2.5 8 [ 29 ] (Yersal et al., 2016) 2013–2014 Turkey Cross-sectional Microscopy, Culture, and PCR Solid 232 6.5 8 [ 20 ] (Zhang et al., 2020) 2018 China Case control PCR Solid 195 13.33 9 [ 26 ] (Pestechian N, 2020) 2014–2019 Iran Cross-sectional Microscopy Solid 187 39 9 [ 72 ] HM; Hematological malignancy, IP; Intestinal parasite, NR; Not reporting, Q Score; quality score, PCR; Polymerase chain reaction

Prevalence of intestinal parasite infection among cancer patients

The random effects model estimated that the pooled prevalence of intestinal parasite infections among cancer patients across various populations was 28.42% (95% CI: 22.22– 34.63) (Fig. 2 ). The diamond shape at the bottom illustrates this pooled prevalence, with its width representing the 95% confidence interval for the estimate. The heterogeneity analysis revealed that there was high-level, significant heterogeneity in our meta-analysis regarding cancer patients (I² = 97.5%, p = 0.000).

Fig. 2 The pooled prevalence of intestinal parasite infection among cancer patients

The pooled prevalence of the most commonly reported intestinal parasitic infections in cancer patients

The random effects model was used to determine the overall prevalence of the most common intestinal parasite infections among cancer patients from various populations. Specifically, Blastocystis hominis had the highest prevalence at 23.13% (95% CI: 15.44–30.81), whereas Cryptosporidium parvum had the lowest prevalence at 3.57% (95% CI: -94.893–102.039) ( Table 2 ). The diamond shape at the bottom represents this overall prevalence, with its width indicating the 95% confidence interval for the estimate. The heterogeneity analysis revealed a high level of significant heterogeneity in our meta-analysis concerning cancer patients (I² = 98.2%, p = 0.000).

Table 2 Prevalence of the most common intestinal parasitic infections among cancer patients, 2024 Types of parasite ES (95% Conf. Interval) I² P = value Blastocyst hominies 23.13% (95% CI: 15.44–30.81) 98.2 0.000 Cryptosporidium parvum 3.57% (95% CI:-94.89–102.04) – 1.000 Giardia lambila 7.06% (95% CI: 4.16–9.96) 93.8 0.000 Entamoeba histolytica 16.04% (95% CI: 6.04–26.04) 98.0 0.000 ES; effect size, I 2 ; Higgins square, p; p value level of significance

Subgroup analysis

Subgroup analysis was conducted to evaluate the prevalence of intestinal parasitic infections among cancer patients, considering various factors, such as study design, year of study, diagnostic methods, geographical location, types of cancer, publication years, sample size, and quality score. The findings revealed that patients with solid tumors presented the highest prevalence of intestinal parasites, at 31.13% (95% CI: 23.93–38.34). In contrast, those with mixed tumors (both solid cancers and hematological malignancies) had the lowest prevalence at 23.26% (95% CI: 13.96–53.95). When the years of study were examined, the prevalence of intestinal infections was similar, with rates of 27.93% (95% CI: 7.49–48.38) for the period from 2006 to 2015 and 28.20% (95% CI: 22.50–33.90) for 2016–2024, despite having varying numbers of studies in each time frame.

With respect to the diagnostic methods used, studies employing culture and PCR techniques demonstrated the highest prevalence of 54.70% (95% CI: 46.39–63.00). Conversely, studies that utilized PCR as the sole diagnostic method reported the lowest prevalence at 13.33% (95% CI: 8.56–18.10). Regarding to geographical location, studies conducted in Africa showed the highest pooled prevalence of intestinal parasites at 41.55% (95% CI: 16.62–66.48), compared to 23.88% (95% CI: 18.38–29.38) in Asia and 26.14% (95% CI: 11.05–41.23) in studies from other continents ( Table 3 ).

Table 3 Subgroup analysis of the IP among cancer patients, 2024 Variables No. of studies prevalence (95% CI) Heterogeneity I 2 (%) P -value IP-Cancer patients 34 28.42% (95% CI: 22.22–34.63) 97.5% < 0.10 Cancer types Solid cancer 19 31.13% (95% CI: 23.93–38.34) 96.0% < 0.10 HM 6 26.89% (95% CI-0.161–53.95) 99.2% < 0.10 Mixed 9 23.26% (95% CI: 13.96–53.95) 96.4% < 0.10 Study design Cross-sectional 18 25.82% (95% CI: 16.86–34.77) 98.1% < 0.10 Case-control 10 28.49% (95% CI: 17.69–39.28) 96.5% < 0.10 Cohort 2 28.38% (95% CI: -12.89–69.63) 98.8% < 0.10 Not reporting 4 42.54% (95% CI: 11.31–73.77) 97.2% < 0.10 Parasitological diagnostic methods Microscopy 15 28.51% (95% CI: 21.225– 35.80) 94.9% < 0.10 Microscopic and PCR 8 18.63% (95% CI: 10.55–26.71) 94.8% < 0.10 Microscopic and Culture 3 47.56% (95% CI: -2.35–97.47) 99.5% < 0.10 PCR 1 13.33% (95% CI: 8.56–18.10) NR < 0.10 Microscopic, Culture, and PCR 2 29.00% (95% CI:-15.582–73.59) 98.7% < 0.10 Microscopic and Serology 4 26.74% (95% CI: 9.85–43.62) 93.9 < 0.10 Culture and PCR 1 54.70% (95% CI: 46.395–63.00) NR < 0.10 Study year 2006–2015 25 27.93% (95% CI: 7.49–48.38) 99.0% < 0.10 2016–2024 9 28.198% (95% CI: 22.50–33.90) 96.0% < 0.10 Geographical locations African continent 7 41.55% (95% CI: 16.62–66.48) 98.8% < 0.10 Asia continent 21 23.88% (95% CI: 18.38–29.38) 95.5% < 0.10 Others continent 6 26.14% (95% CI: 11.05–41.23) 95.9% < 0.10 CI: confidence interval, HM; Hematological malignancy, IP: intestinal parasite, others: Europe and Latin America, PCR; polymerase chain reaction

Additionally, we conducted a meta-regression analysis in conjunction with a subgroup analysis to identify possible sources of heterogeneity. Our meta-regression results did not reveal a statistically significant association between the prevalence of intestinal parasite infection in cancer patients and quantitative variables such as publication year, sample size, and quality score. Therefore, publication year (regression coefficient 1.094631, p = 0.673), sample size (regression coefficient 0.9988639, p = 0.833), and quality score (regression coefficient 1.855211, p = 0.527) were not considered causes of variability in the intestinal parasite infection rate in cancer patients (Table 4 ).

Table 4 Meta-regression by publication year, sample size, and quality score for the outcome of IP among cancer patients worldwide, 2024 Variables Coef. Std. Err. t P >|t| [95% Conf. Interval] Publication year 1.094631 0.2322226 0.43 0.673 (0.7101638–1.687239) Sample size 0.9988639 0.0053335 -0.21 0.833 (0.9880587–1.009787) Quality score 1.855211 1.791666 0.64 0.527 (0.2594565–13.26545) Coef; coefficient, Conf. Interval; confidence interval, IP; intestinal parasite, P; p-value, Std. Err.; standard error, t; t-statistic

Publication bias

Egger’s test and funnel plots were employed independently to assess potential publication bias across the studies. The current study indicated a significant level of publication bias. The results from Egger’s regression test demonstrated a substantial bias, reporting a value of 8.86% (95% CI: (4.9–12.79), p = 0.000) (Table 5 ). The asymmetrical distribution of the funnel plot revealed the presence of publication bias across the included primary studies (Fig. 3 ).

Table 5 Publication bias according to egger’s test Std_Eff Coef. Std. Err. t P > t [95% Conf. Interval] Slope -5.179103 5.29811 -0.98 0.335 (-15.95819–5.599983) Bias 8.863219 1.912876 4.63 0.000 (4.966818–12.75962) Coef; coefficient, Conf. Interval; confidence interval, P; p-value, Std. Err.; standard error, t; t-statistic

Trim-and-fill analysis was also performed to assess and adjust for publication bias on the basis of the assumption that the effect sizes of all the studies are normally distributed around the center of a funnel plot in the absence of publication bias. As a result, we conducted trimming and filling analyses to reduce and adjust for publication bias in the included primary articles. Therefore, after correction, the estimated pooled prevalence was 11.40 (95% CI 4.42–18.38), p = 0.001 (Fig. 4 ).

Fig. 3 Funnel plot showing the publication bias

Fig. 4 Funnel plot showing the random effect trim and fill analysis results

Sensitivity analysis

The sensitivity analysis demonstrated that excluding each of the thirty-four studies with ORs, there was no significant change in the final OR. Moreover, the overall pooled prevalence of intestinal parasite infections in cancer patients ranged from 26.23% (95% CI: 21.33–31.14) to 29.24% (95% CI: 22.82–35.64) when each article was removed from the analysis (Table 6 ).

Table 6 Leave-one-out meta-analysis of IP among cancer patients, 2024 A one-leave-out analysis Estimate (95% confidence interval) Heterogeneity I 2 (%) p -value (Abdel-Magied et al., 2016) 26.23 (21.33 – 31.14) 95.9 0.000 (Ali et al., 2022) 27.71 (21.49 – 33.92) 97.5 0.000 (Bahadorizadeh et al., 2024) 28.33 (22.01 – 34.65) 97.6 0.000 (Banihashemi et al., 2020) 29.208 (22.73 – 35.69 ) 97.4 0.000 (Berahmat et al., 2017) 29.22 (22.82 – 35.64 ) 97.5 0.000 (Bora et al., 2016) 27.18 (20.98 – 33.38) 97.5 0.000 (El-Badry et al., 2019) 29.13 (22.72 – 35.55) 97.6 0.000 (Esteghamati et al., 2019) 28.50 (22.18–34.83 ) 97.6 0.000 (Heydari et al., 2021) 28.56 (22.24 – 34.87) 97.6 0.000 (Inah et al., 2022) 28.22 (21.92 – 34.52) 97.6 0.000 (Jeske et al., 2017) 27.44 (21.26 – 33.61) 97.5 0.000 (Kaplan et al., 2020) 28.11 (21.83 – 34.39) 97.6 0.000 (Knapp et al., 2019) 27.76 (21.56 – 33.96) 97.5 0.000 (Labania et al., 2023) 27.42 (21.23 – 33.62) 97.5 0.000 (Lanocha et al., 2022) 28.80 (22.47 – 35.12) 97.6 0.000 (Machado et al., 2008) 28.54 ( 22.24 – 34.841) 97.6 0.000 (Mahmoudi et al., 2020) 29.01 ( 22.46 – 35.56) 97.6 0.000 (Mohammadi-Ghalehbin et al., 2017) 29.01 (22.64 – 35.39) 97.6 0.000 (Mohamed et al., 2017) 27.60 (21.44 – 33.75) 97.5 0.000 (Mirzaei et al., 2021) 28.958 (22.53 – 35.39) 97.6 0.000 (Nasir et al., 2020) 28.82 (22.35 – 35.28) 97.6 0.000 (Neamah, 2021) 28.55 (22.12 – 34.98) 97.6 0.000 (Nooshadokht et al., 2017) 28.83 (22.49 – 35.16) 97.6 0.000 (Salehi et al., 2018) 28.66 (22.29 – 35.02) 97.6 0.000 (Salehi Kahyesh et al., 2020) 28.14 (21.86 – 34.43) 97.6 0.000 (Seleem et al., 2024) 27.92 (21.67 – 34.18) 97.5 0.000 (Singh et al., 2024) 29.08 (22.70 – 35.46) 97.6 0.000 (Siti Farah Norasyikeen et al., 2024) 28.31 (22.00 – 34.63 ) 97.6 0.000 (Sitotaw et al., 2022) 28.76 (22.44 – 35.08) 97.6 0.000 (Sulzyc-Bielicka et al., 2021) 28.94 (22.57 – 35.32) 97.6 0.000 (Toychiev et al., 2018) 29.12 (22.66 – 35.57) 97.6 0.000 (Yersal et al., 2016) 29.15 (22.67 – 35.64) 97.5 0.000 (Zhang et al., 2020) 28.922 (22.49 – 35.35) 97.6 0.000 (Pestechian N, 2020) 28.09 (21.82 – 34.36) 97.5 0.000 I 2 (%); Higgins square, IP; intestinal parasite

Discussion

Intestinal parasitic infections remain a significant global health issue, particularly in developing countries, where they contribute to considerable morbidity and mortality. This risk is heightened among immunocompromised individuals, especially cancer patients [ 41 ], who can face serious complications if these infections are not diagnosed and treated promptly [ 24 ]. Moreover, cancer patients are particularly susceptible to opportunistic infections. According to a systematic review and meta-analysis on Giardia intestinalis conducted globally, these patients are 1.24 times more likely to develop infections, placing them at increased risk [ 42 , 43 ]. Approximately one-quarter of the global population lives without adequate hygiene and diagnostic resources, which leads to the underestimation and prevalence of chronic parasitic infections, which are major contributors to worldwide morbidity and mortality [ 44 , 45 ].

The current study revealed that the overall prevalence of intestinal parasite infections in cancer patients was 28.42% (95% CI: 22.22–34.63), accompanied by significant heterogeneity (I² = 97.5%, p = 0.000). This finding aligns with earlier research, including a meta-analysis on G. duodenalis infections in cancer patients in Iran, which reported a pooled prevalence of 6.9% [ 43 ], and supported by single studies conducted in Iran, which reported a prevalence of 6.7% [ 4 ]), and a prevalence of 20% in immunocompetent individuals in India [ 46 ], alongside another study in India, which reported 8.5% [ 47 ]. The difference between the current and other primary studies might be due to study population groups (immunocompetent) the immune system acts quickly and efficiently to either prevent parasite infection or limit its severity and duration. As a result, parasite prevalence and symptom severity tend to be lower [ 48 ]. The discrepancy between the current meta-analysis and previous meta-analyses conducted in Iran may be attributed to differences in the number of studies included, as well as the narrower focus of those studies on single-parasite infections. In contrast, our analysis provides a more comprehensive assessment of overall intestinal parasitic infections. The findings indicate that nearly one-third of cancer patients are at risk of these infections, posing a substantial challenge to effective cancer management and efforts to improve patients’ quality of life [ 49 ].

In contrast, the pooled prevalence in the current study was lower than that reported in studies conducted in Iraq (54.0%) [ 50 ], and Yemen (51.8%) [ 51 ]. The differences observed between the current study and earlier research may be due to several factors; those studies often focused on selective populations, specifically diarrheic cancer patients undergoing chemotherapy, and developed more sensitive and specific diagnostic methods for cryptosporidiosis, particularly in the study conducted in Iraq the study setting was in rural, surrounding with the urban area [ 52 ]. Overall, the increased prevalence of studies in Iraq and Yemen could be attributed to various factors, including lifestyle choices, overall health status, immune function, types of treatments administered, environmental pollution (both indoors and outdoors), personal hygiene practices, health culture regarding infectious diseases, economic conditions, and water management and sanitation practices. These factors contribute to the potential severity and chronic nature of cryptosporidiosis [ 53 , 54 ].

This study included several articles examining various intestinal helminth and protozoan parasites, among which Blastocystis hominis , Cryptosporidium parvum , and Giardia lamblia were the most commonly found in cancer patients. The computed pooled prevalence of Blastocystis hominis infection among the 2,813 study participants with cancer was 23.13%. This prevalence was higher than that reported in a systematic review and meta-analysis conducted in Iran, which reported a global pooled prevalence of 9% for Blastocystis hominis [ 55 ], 12.5% in Iran [ 56 ], and 9.18% in Spain [ 57 ] among non-cancer patients. The discrepancies between these studies may be attributed to variations in the number of articles reviewed and the sample sizes used.

This review revealed significant heterogeneity (I 2 = 97.5%) among the included studies. A subgroup analysis was performed to determine the sources of heterogeneity. As a result, the prevalence of intestinal parasite infections among cancer patients varies significantly between diagnostic methods, ranging from 54.70% (95% CI: 46.39–63.00) according to both culture and PCR and 13.33% (95% CI: 8.56–18.10) according to studies that used only PCR. The variation observed among diagnostic methods may be attributed to culture techniques that foster the growth of microorganisms in a controlled environment. This process can amplify even small numbers of organisms while selectively inhibiting others, which aids in confirming the target microorganism and enhances detection [ 58 ]. Moreover, PCR is renowned for its high sensitivity, allowing it to identify minute quantities of DNA, thus enabling the detection of organisms even at extremely low concentrations. Both methods can also identify viable and non-viable organisms, contributing to the high detection rates observed with culture and PCR techniques [ 59 ].

Subgroup analysis of intestinal parasites among cancer patients by study year revealed consistent findings, with prevalence rates of 27.93% (95% CI: 7.49–48.38) for the period 2006–2015 and 28.20% (95% CI: 22.50–33.90) for 2016–2024. This similarity may be attributed to factors such as sustained awareness, improved hygiene practices, enhanced access to healthcare, effective public health interventions, advancements in diagnosis and treatment, and lifestyle and dietary changes over time [ 60 ].

Subgroup analysis of intestinal parasites among cancer patients revealed that those with solid tumors presented the highest prevalence, at 31.13% (95% CI: 23.93–38.34) than hematological malignancy. This difference may be partially attributed to the inclusion of 19 studies with large sample sizes, and sample size differences, selection bias, or regional variations in parasite prevalence, which could improve the detection of such infections. Additionally, patients with solid cancers often undergo chemotherapy or radiotherapy, both of which can compromise immune function and disrupt the gut microbiota, increasing susceptibility to opportunistic parasitic colonization [ 61 ]. The prolonged hospitalization, use of broad-spectrum antibiotics [ 62 ], malnutrition, particularly prevalent among patients with gastrointestinal tumors, is another contributing factors [ 63 , 64 ].

Regarding to geographical location, studies conducted in Africa showed the highest pooled prevalence of intestinal parasites at 41.55% (95% CI: 16.62–66.48), compared to 23.88% (95% CI: 18.38–29.38) in Asia and 26.14% (95% CI: 11.05–41.23) in studies from other continents.

This discrepancy may stem from variations in diagnostic capabilities, access to clean water and sanitation, healthcare infrastructure, and cancer treatment protocols across regions, all of which likely contributed to the observed heterogeneity. These factors may also reflect limited access to healthcare services and preventive measures [ 65 ].

Strengths and limitations of the study

The present work aimed to provide a clear pooled estimate of the prevalence of intestinal parasite infection in cancer patients on the basis of the current status of science, which may be elucidated in the near future through extensive research. This review has several limitations. First, there is a lack of sufficient systematic reviews and meta-analyses on intestinal parasitic infections among cancer patients, making comparisons challenging. Second, the study shows evidence of significant publication bias. Limiting the inclusion criteria to English-language articles may have excluded relevant studies published in other languages, introducing selection bias and potentially reducing the comprehensiveness and applicability of the findings. However, Future studies should aim to include multilingual sources to minimize this bias. Finally, substantial heterogeneity was observed in the meta-analysis, which could impact the reliability of the pooled prevalence estimates.

Conclusion

To our knowledge, this is the first global systematic review and meta-analysis examining the prevalence of intestinal parasitic infections in cancer patients. The findings reveal a high pooled prevalence in this vulnerable group, with notable heterogeneity. The results underscore the importance of routine screening for intestinal parasites in immunocompromised patients and suggest a link to opportunistic infections like Blastocystis . For better clinical utility, we recommend standardized screening intervals, multiple stool sample collection, occult blood testing, use molecular diagnostics (PCR) alongside microscopy for better accuracy, and risk-based stratification by cancer type and treatment. These evidence-based strategies would transform general recommendations into an actionable clinical framework and enable oncologists to immediately implement practices. Future prospective cohort studies are needed to clarify causality and guide targeted prevention strategies.

Electronic supplementary material

Below is the link to the electronic supplementary material.

Supplementary Material 1: S1 Table: PRISMA 2020 checklist (docx).

Supplementary Material 2: S2 Table: JBI quality assessment (docx).

Publisher’s note

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Acknowledgements

Not applicable.

Author contributions

Conceptualization: YMW and AD. Data curation: YMW and GAA. Formal analysis: YMW and AS. Methodology: YMW, AS, GAA, GG, MA, MT, AD and ZY. Software: YMW, AS, and BG, MT. Supervision: GAA, GG, BMM, and AS. Validation: YMW, ND and MA. Writing original draft: YMW, AS, ZY, GG, BG, and GAA. Writing, review & editing: YMW, MA, BMM, AD, and GG. All the authors read and approved the final manuscript.

Funding

No funding.

Data availability

All the data and its supporting files are within the manuscript and are available from the corresponding author upon a reasonable request.

Declarations

Ethics approval and consent to participate

Not applicable.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.

Abbreviations

Hematological Malignancies

Intestinal Parasites

Odd Ratios

Preferred Reporting Items for Systematic Reviews and Meta-Analyses

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